The present invention generally relates to a rotary piston engine and, more particularly, to a gas sealing mechanism in a rotary piston engine.
A typical rotary piston engine has a peripheral wall, having a trochoidal inner surface, and axially spaced end walls interconnected to each other with said peripheral wall positioned therebetween, thereby defining an engine cavity in said housing structure. A substantially triangular rotor having arcuate flanks and apex portions equal in number to said flanks is rotatably mounted within the engine cavity on an eccentric portion of a power output shaft, journalled in the end walls, for eccentric rotation about the shaft. The rotor within the engine cavity divides said engine cavity into a plurality of working chambers which vary in volume during the planetary motion of said rotor with said apex portions held in sliding engagement with the trochoidal inner surface of the peripheral wall through corresponding apex seals. In each of these working chambers there takes place a four cycle internal combustion process which includes intake, compression, combustion and exhaust strokes. An air-fuel mixture is adapted to be introduced into one of the working chambers during the intake stroke through an intake port formed in one or both of the end walls. The rotor is generally cooled by oil flowing through the power output shaft and then the eccentric portion thereof, a controlled amount of which is allowed to leak into a definite area within a space between end faces of the rotor and the end walls for the purpose of lubrication.
In the rotary piston engine of the construction described above, it is also well known that, in order to block the path of leakage of gas from any one of the working chambers into the space between the end faces of the rotor and the end walls and also the path of leakage of oil from the eccentric portion of the shaft into the same space, sealing means are employed on each end face of the rotor.
More specifically, the rotor has in each end face at least one set of side seal grooves, each extending so as to follow the curvature of the rotor flank, and also at least one oil seal groove in coaxial relation to the eccentric portion of the power output shaft and situated inside the side seal grooves. Each of the side seal grooves accommodates therein a side seal and a spring element, such as a corrugated wire spring, for outwardly biasing the side seal to cause the latter to slidingly engage the corresponding end wall, while the opposed end portions of the side seal are operatively engaged with two of the corner seals which also receive one end of the apex seals on the respective apex portions of the rotor. Similarly, the oil seal groove accommodates therein an oil seal ring and a spring element for outwardly biasing the oil seal ring to cause the latter to slidingly engage the corresponding end wall and which is held in position by a so-called O-ring, that is, a retainer ring which serves not only to retain the oil seal ring in position, but also to make a contribution to oil sealing.
In practice, a blowby gas, which is at an elevated temperature and containing unburned fuel components of the combustion gas which, when they accumulate, tend to form sludge which sticks to the engine parts which are exposed to the passage of the blowby gas, tends to enter past the side seals into the space under the influence of the explosive force developed upon combustion of the air-fuel mixture within the working chamber during the combustion stroke. When the rotary piston engine has been operated for a relatively great total period of time, the blowby gas causes a noticeable adverse influence on the engine parts and particularly on the O-ring, which is made of elastic rubber material, and bearing elements forming the bearing mechanism by which the rotor is mounted on the eccentric portion of the power output shaft. In other words, the O-ring tends to deteriorate under the influence of the elevated temperature of the blowby gas and the contact with the unburned fuel components while the oil seal ring and the bearing elements tend to be damaged by the sludge sticking thereto.
In order to minimize the adverse influence of the blowby gas on the engine parts, for example, Japanese Patent Publication (Unexamined) No. 10909/1975 which has been laid open to public inspection discloses the provision of gas groove means formed in the rotor on each end face thereof and between the side seals and the oil seal ring so that the blowby gas having entered the space past the side seals can be trapped, or otherwise collected, in said gas groove means. With the gas groove means such as disclosed in the publication referred to above, the adverse influence of the blowby gas on the engine parts can be minimized to a certain extent. However, there is still room for improvement in minimizing such adverse influence.